Why the ESB PTX Example does't have any clock config

Question

The Enhanced ShockBurst PTX Project just inits the ESB and start transmitting without ever configing either of the 16MHz or 32kHz clocks (none that I can see at least). 
 Questions: 
 
 
 Seems like both the 16MHz and the 32kHz clocks are disabled. True? 
 
 
 What clock is ESB running from then? Does it auto init the 16MHz clock? 
 
 
 As long as I use a peripheral like SPI-Slave, or GPIOs, I should not need any clock running? 
 
 
 If neither clock is running, how does this affect my power consumption? Should be super-low if I don't transmit anything, and just _WFI() until I receive on SPI-Salve, correct? 
 
 
 Thanks

Asbjørn · Accepted Answer

No, the 16 Mhz will be started by the ESB library when needed. It's hidden inside the library functions, but if you probe on the crystal, you'll see that it's started when the radio is transmitting. The 32 kHz is not needed for radio operation and will only be started if you need it from your application. 
 Internal 16 Mhz RC oscillator for the MCU and external 16 MHz will be enabled when radio need it. 
 Yes, SPI requires 16 MHz. You can request it to be started when you need it. 
 You want to power down as soon as possible to save power. Powering down also means shutting down the clock sources. If you want to use the 32 kHz as a RTC source, that would be the lowest power consuming way to implement wakeup on timer.

Why the ESB PTX Example does't have any clock config

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